A typical problem in a metallic halide laser is the control of the metallic halide vapor density within the laser. As is well known to those familiar with metallic halide lasers, the energy and peak power per discharge pulse is strongly dependent upon the metallic halide vapor density within the laser. Maximum power output can be obtained only over a very narrow range of vapor densities. One conventional way of controlling the vapor density is by a slow thermal diffusion of vapors from a metallic halide source located in either the laser discharge tube itself or in a separately heated reservoir. This method is critically dependent on the temperature of the metallic halide which can vary significantly.
A typical metallic halide laser, such as a copper halide laser, utilizes a continuous flow of a buffer gas such as neon through the laser tube. As a result, the copper halide vapor must be continuously supplied in order to maintain an optimum vapor density in the laser discharge. In one conventional system, a copper halide salt is placed along the bottom of the laser tube and the tube placed inside an oven having a uniform temperature. At very low pulse repetition rates, the temperature of the copper halide, and thus its vapor pressure, can be adjusted by changing the oven temperature. However, at higher pulse repetition rates it has been found that the copper halide vapor pressure and rate of vaporization are most dependent on the pulse discharge and can not be independently controlled. The present invention solves the above problems by providing a method and apparatus for continuously controlling the metallic halide vapor density in the laser tube regardless of temperature changes in the metallic halide vapor source.